Jump to content
sofakng

Need help building Pentium MMX VRM module (re: IBM PC)

Recommended Posts

I know this is questionable whether it belongs here or not, but seeing so many electronic projects here (and so many intelligent people!) I'm hoping that somebody might be able to help.

 

I've picked up an old IBM PC 350 computer which supported up to Pentium MMX CPUs.  However, an external voltage regulator board was required and only included in models that included those CPUs from the factory.  

 

The BIOS on all models seem to support the MMX CPUs and they work fine but without the regulator the Vcore is 3.3v instead of 2.8v.

 

I've posted more information (including multimeter measurements and datasheets) over at the Vogons forum: https://www.vogons.org/viewtopic.php?f=46&t=81718

If anybody is willing to help me at all it would be very greatly appreciated!

Share this post


Link to post
Share on other sites
Posted (edited)

The manual says it is only P54C. (Non MMX).

 

There is a pinout difference between P54C and P55C. One is Socket 5, the other is Socket 7.

 

You would need a full interposer, due to Socket 7 have 1 additional pin (in addition to the 3.3v voltage)

 

Something like a powerleap PL-54C/MMX

 

If you were to build one... (which I would not recommend)-- you would need a voltage regulator IC designed for that,(Datasheet), along with some PCB, and one each LIF socket 5, and ZIF socket 7.

 

You use the LIF as the base to interface with the motherboard's ZIF, and the new ZIF to accept the new CPU.  Route the Socket 5 voltage and clock lines to the regulator IC, and the corrected voltages and clock to the socket 7.

 

You would also need some crystal chips, etc-- the divide the clock suitably.

 

It is beyond my skill, and I would strongly discourage trying to build one.  I would instead suggest hunting for something like the Powerleap interposer.

 

 

Edited by wierd_w
  • Like 1

Share this post


Link to post
Share on other sites

PowerLeap makes a good product. But they were also caught in that capacitor thing. So if you buy anything from that era, replace the caps. All my slockets and interposers, regulators, and converters needed their electrolytics replaced early.

  • Like 1

Share this post


Link to post
Share on other sites

$200?!!?! It's a workable solution and quality product. But I'd hate to see the OP pay $200 for what was once outmoded e-waste. Especially when the seller likely got these for free or under $30. These things were likely put in systems and then those systems put curbside. Or sent to china for stripdown. Or given to others that strip them for parts - something that's increasingly happening.

 

It's nothing new. Lot's of sellers trying to make bigbux. Sucking in nostalgia seekers. Because they can. 'Tis like that in many hobbies. And I'm beginning a one-man crusade against high priced parts. Just don't buy them at these exorbitant prices.

  • Like 2

Share this post


Link to post
Share on other sites
Posted (edited)

Agreed the price is a rip, but the normal places for a sensible price are dry.

 

Those things are indeed rare, it seems.  (If the product is indeed actually rare-- like those unobtanium MCA soundblaster clones-- the high prices become unavoidable. After a certain break-even point, a market for anacronistic parts crops up, and you get stuff like the noise barker getting made and sold.  If there is a market for interposers, somebody will start making them, should the prices become high enough.)

Edited by wierd_w

Share this post


Link to post
Share on other sites
Posted (edited)

If this was me. And I was building for practical usage I would totally skip it. Find another solution. But for nostalgia, I might consider it.

Edited by Keatah

Share this post


Link to post
Share on other sites

Agreed.  I would put a 133 P54C in, and call it a day.

 

Use the resulting system to play late-era DOS titles, like wingcommander 3, X-wing, Tie-Fighter, and the like.  Things that can profit from having a PCI video card, and a pentium chip-- but still DOS, and thus not likely to need MMX instructions anyway.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...